Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calcium/calmodulin dependent protein kinase II (CaMKII) is a multifunctional serine/threonine protein kinase. We have created a calcium/calmodulin independent form of this enzyme by truncation. Expression of this enzyme fragment in a rabbit reticulocyte lysate yields a constitutive enzyme with specific activity similar to the activated native enzyme. We have established mammalian cell lines that transiently express this constitutive enzyme using the glucocorticoid-inducible mouse mammary tumor virus long terminal repeat. The transient increase in kinase activity results in a complete cessation of cell cycle progression. This block develops as a consequence of a specific arrest of the cell cycle in G2. During the block, increases in histone H1 kinase activity present in p13 beads or anti-cdc2 immunoprecipitates are seen in parallel with the accumulation of cells at G2, arguing that the arrest is not due to a failure to activate cdc2 as a histone H1 kinase. These results suggest that other changes in serine/threonine protein phosphorylation besides those involved in activation of cdc2 as a histone H1 kinase may be necessary for proper G2-M transition.
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PMID:Expression of a constitutive form of calcium/calmodulin dependent protein kinase II leads to arrest of the cell cycle in G2. 137 61

Mitosis-specific phosphorylation by cdc2 kinase causes nonmuscle caldesmon to dissociate from microfilaments (Yamashiro, S., Yamakita, Y., Ishikawa, R., and Matsumura, F. (1990) Nature 344, 675-678; Yamashiro, S., Yamakita, Y., Hosoya, H., and Matsumura, F. (1991) Nature 349, 169-172). To explore the function of mitosis-specific phosphorylation of caldesmon, in vivo- and in vitro-phosphorylated caldesmons have been characterized. We have found that both in vivo and in vitro phosphorylation of caldesmon causes similar changes in the properties, including reduction in actin, calmodulin, and myosin binding of caldesmon, and a decrease in the inhibition of actomyosin ATPase by caldesmon. Rat non-muscle caldesmon is phosphorylated in vitro up to a ratio of 7 mol/mol of protein. Actin-binding constants of both a high affinity (K a = 1.2 x 10(7) M-1) and a low affinity (K a = 1 x 10(6) M-1) site of unphosphorylated caldesmon are reduced to less than 10(5) M-1 with 5 mol of phosphate incorporation per mol of protein. Actin-bound caldesmon can be phosphorylated by cdc2 kinase, which results in the dissociation of caldesmon from F-actin. Caldesmon has a second myosin-binding site in the C terminus, in addition to the N terminus myosin-binding domain previously reported, because the bacterially expressed C terminus of caldesmon shows binding to myosin. Phosphorylation of the C-terminal fragments decreases their myosin-binding affinity as observed with intact caldesmon. These results suggest that caldesmon loses most of its in vitro functions during mitosis as a result of phosphorylation, which may be required for the reorganization of microfilaments during mitosis.
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PMID:Characterization of mitotically phosphorylated caldesmon. 153 4

Nonmuscle caldesmon from bovine brain bound to microtubules with a stoichiometry of five tubulin dimers to one molecule of caldesmon with values of Ka 4.5 x 10(5) M-1. The binding of caldesmon to microtubules was inhibited in the presence of Ca2+ and calmodulin. The phosphorylation of caldesmon by cdc2 kinase also eliminated the microtubule-binding activity. These results suggest that caldesmon may play a physiological role in the functions of microtubules.
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PMID:The binding of nonmuscle caldesmon from brain to microtubules. Regulations by Ca(2+)-calmodulin and cdc2 kinase. 154 74

One of the profound changes in cellular morphology during mitosis is a massive alteration in the organization of microfilament cytoskeleton. It has been recently discovered that nonmuscle caldesmon, an actin and calmodulin binding microfilament-associated protein of relative molecular mass Mr = 83,000, is dissociated from microfilaments during mitosis, apparently as a consequence of mitosis-specific phosphorylation. cdc2 kinase, which is a catalytic subunit of MPF (maturation or mitosis promoting factor), is found to be responsible for the mitosis-specific phosphorylation of caldesmon. Because caldesmon is implicated in the regulation of actin myosin interactions and/or microfilament organization, these results suggest that cdc2 kinase directly affects microfilament re-organization during mitosis.
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PMID:Mitosis-specific phosphorylation of caldesmon: possible molecular mechanism of cell rounding during mitosis. 177 11

We sought the mammalian neurofilament tail domain-specific kinase. Several well known kinases including cAMP-dependent protein kinase, protein kinase C, Ca(2+)-calmodulin-dependent protein kinase II, casein kinase I, and casein kinase II phosphorylated the high (NF-H) and middle molecular mass subunit (NF-M) of bovine neurofilaments, but they did not reduced the electrophoretic mobility of the dephosphorylated form of NF-M and NF-H by phosphorylation nor was the amount of phosphorylation increased by dephosphorylation of NF proteins, indicating that the phosphorylation sites by these kinases are not major in vivo phosphorylation sites at the tail domain. In contrast, cdc2 kinase phosphorylated specifically the dephosphorylated form of NF-H. 4 mol of phosphates were incorporated per mol of NF-H and this phosphorylation returned the electrophoretic mobility of the dephosphorylated form of NF-H to the position of the isolated, fully phosphorylated form of NF-H. Furthermore, the phosphorylation by cdc2 kinase dissociated the binding of dephosphorylated NF-H to microtubules. Phosphorylation sites were located at the carboxyl-terminal tail domain. The KSPXK motif, but not KSPXX, in the repetitive sequence was suggested to be the phosphorylation site by using synthetic peptides.
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PMID:Phosphorylation of neurofilament H subunit at the tail domain by CDC2 kinase dissociates the association to microtubules. 193 2

One of the profound changes in cellular morphology which occurs during mitosis is a massive alteration in the organization of the microfilament cytoskeleton. This change, together with other mitotic events including nuclear membrane breakdown, chromosome condensation and formation of mitotic spindles, is induced by a molecular complex called maturation promoting factor. This consists of at least two subunits, a polypeptide of relative molecular mass 45,000-62,000 (Mr 45-62K) known as cyclin, and a 34K catalytic subunit which has serine/threonine kinase activity and is known as cdc2 kinase. Non-muscle caldesmon, an 83K actin- and calmodulin-binding protein, is dissociated from microfilaments during mitosis, apparently as a consequence of mitosis-specific phosphorylation. We now report that cdc2 kinase phosphorylates caldesmon in vitro principally at the same sites as those phosphorylated in vivo during mitosis, and that phosphorylation reduces the binding affinity of caldesmon for both actin and calmodulin. Because caldesmon inhibits actomyosin ATPase, our results suggest that cdc2 kinase directly causes microfilament reorganization during mitosis.
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PMID:Phosphorylation of non-muscle caldesmon by p34cdc2 kinase during mitosis. 198 9

A recent report that mitosis-specific phosphorylation causes the nonmuscle caldesmon to dissociate from microfilaments (Yamashiro, S., Yamakita, Y., Ishikawa, R., and Matsumura, F. (1990) Nature 344, 675-678) suggests that this process may contribute to the major structural reorganization of the eukaryotic cell at mitosis. In this study we have demonstrated that smooth muscle caldesmon is phosphorylated in vitro by cdc2 kinase from mitotic phase HeLa cells to 1.2 mol of phosphate/mol of caldesmon. Tryptic maps showed three major phosphorylated spots and approximately equal amounts of phosphorylated Ser and Thr were identified. F-actin or calmodulin in the presence of Ca2+ blocks the phosphorylation of caldesmon. Phosphorylation of caldesmon greatly reduced its binding to F-actin. The phosphorylation sites were located in a 10,000-Da CnBr fragment at the COOH-terminal end of the caldesmon molecule known to house the binding sites for actin and calmodulin (Bartegi A., Fattoum, A., Derancourt, J., and Kassab, R. (1990) J. Biol. Chem. 265, 15231-15238). Our finding supports the model that phosphorylation of caldesmon by cdc2 kinase at mitosis may contribute to the disassembly of the microfilament bundles during prophase.
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PMID:Phosphorylation of caldesmon by cdc2 kinase. 201 82

We identified two major substrates for the proline-directed protein kinases--cdc2 kinase and tau protein kinase II (TPKII)--in the cytosol fraction from rat brains. The molecular masses of the proteins were 80 and 46 kDa. Because the 80-kDa protein was phosphorylated by protein kinase C and was heat stable, we examined the possibility that the protein might be myristoylated alanine-rich C kinase substrate (MARCKS). On the basis of a comparison between the properties of the 80-kDa protein and purified MARCKS, we concluded that the 80-kDa protein is indeed MARCKS. The amounts of phosphate incorporated into MARCKS by protein kinase C, cdc2 kinase, and TPKII were 1.7, 1.4, and 0.6 mol/mol of the protein, respectively. Two-dimensional tryptic peptide mapping indicated that phosphorylation sites by protein kinase C and proline-directed protein kinases completely differed. Only the seryl residue was phosphorylated by protein kinase C, whereas both seryl and threonyl residues were phosphorylated by cdc2 kinase and TPKII. Phosphorylation of MARCKS by protein kinase C inhibited the binding to calmodulin, whereas phosphorylation by cdc2 kinase and TPKII significantly increased the binding to calmodulin. The holoenzyme of protein phosphatase 2A dephosphorylated MARCKS that had been phosphorylated by protein kinase C, cdc2 kinase, or TPKII, whereas calcineurin was unable to dephosphorylate it. These results suggest that cdc2 kinase and TPKII regulate the functions of MARCKS in different ways from protein kinase C.
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PMID:Phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS) by proline-directed protein kinases and its dephosphorylation. 761 38

Intracellular signaling by the second messenger Ca2+ through its receptor calmodulin (CaM) regulates cell function via the activation of CaM-dependent enzymes. Previous studies have shown that cell cycle progression at G1/S and G2/M is sensitive to intracellular CaM levels. However, little is known about the CaM-regulated enzymes involved. Protein phosphorylation has been shown to be important for cell-cycle regulation. Because CaM regulates several protein kinases, and at least one protein phosphatase, our studies are focusing on the roles of these enzymes within the cell cycle. As an initial approach to this problem, cDNAs encoding either normal or mutant calcium/calmodulin kinase II (CaMKII) have been expressed in Schizosaccharomyces pombe. The results show that overexpression of a constitutively active mutant CaMKII caused cell-cycle arrest in G2. Arrest was associated with a failure to activate the p34/cdc2 protein kinase. Expression of the mutant CaMKII in strains of S. pombe with altered timing of mitosis revealed that this effect is not mediated either by cdc25+ or wee1+, suggesting that CaMKII may regulate G2/M progression by another mechanism.
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PMID:Inhibition of G2/M progression in Schizosaccharomyces pombe by a mutant calmodulin kinase II with constitutive activity. 781 47

We identified the phosphorylation sites of glial fibrillary acidic protein (GFAP) for cdc2 kinase and Ca(2+)-calmodulin (CaM)-dependent protein kinase II. GFAP was phosphorylated to approximately 0.2 mol of phosphate/mol of GFAP by cdc2 kinase, and this phosphorylation did not induce disassembly of the filament structure. On the other hand, GFAP was phosphorylated to approximately 1.9 mol of phosphate/mol of GFAP by Ca(2+)-CaM-dependent protein kinase II, and this phosphorylation did induce disassembly of the filament. Sequential analysis of the purified phosphopeptides revealed that only Ser8 on GFAP was phosphorylated by cdc2 kinase, whereas Ser13, Ser17, Ser34, and Ser389 on GFAP were phosphorylated by Ca(2+)-CaM-dependent protein kinase II.
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PMID:Identification of phosphorylation sites on glial fibrillary acidic protein for cdc2 kinase and Ca(2+)-calmodulin-dependent protein kinase II. 782 64


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